The battle for this season's Heineken Cup appears to be simmering nicely following the latest thrilling round of pool matches.

Some familiar faces are once again leading the chase for Europe's top club prize with four-time champions Toulouse, perennial title challengers Munster and defending champions Leinster among the unbeaten sides but nothing is decided as yet and with the pool stage only having just reached the halfway stage.

Toulouse's emphatic victory over Harlequins in a much-hyped Pool 6 showdown at The Stoop was arguably the most impressive showing and underlined the French side's undoubted class. The Top 14 giants brought Quins crashing back down to earth and ended their unbeaten start to the season thanks to a 21-10 scoreline that hints at their superiority but does not fully illustrate their dominant display. The visitors bullied an under-strength Quins side tipped by many for big things but found wanting against a Toulouse outfit that looked assured and threatening throughout with No.8 Louis Picamoles an outstanding performer.

The failure to secure a bonus point is set to hurt Quins just as much as the result but they remain in the hunt for the last eight - as do Pool 6 rivals Gloucester who breathed life into their campaign with a narrow 14-10 victory over Connacht in Galway. A repeat win on home soil next weekend will do them no harm but you expect Toulouse and Quins to dominate as the race hots up in the New Year.

Munster's narrow 17-14 victory over Scarlets in their Pool 1 clash in Llanelli is likely to prove as pivotal as Toulouse's notable triumph. The hosts were left to rue a host of missed chances that leave them facing an even stiffer task in Limerick next weekend. As has been the way this season, veteran fly-half Ronan O'Gara was a key factor for the Munstermen - landing 12 points to celebrate his 100th tournament appearance in style.

Elsewhere in Pool 1, Northampton's hopes of getting anywhere near to replicating their final appearance last season appear to be hanging by a thread after a crushing 41-22 reverse at the hands of Castres - their third straight loss of the campaign. Yellow cards for fly-half Stephen Myler and flanker Tom Wood did not help the Saints' cause with Castres playmaker Romain Teulet happy to make them pay for their indiscipline with a 21-point haul that kept his side's own euro hopes alive.

Yellow cards also proved costly at the Stade Marcel Michelin where hooker George Chuter and centre Manu Tuilagi were given their marching orders during a fiery clash against Clermont Auvergne. The hosts kept their heads to register a 30-12 victory that extended their two-year unbeaten run at home and propelled them to the top of Pool 4. As a result the Leicester will be up against it when they play host to Les Jaunards next weekend with Ulster's bonus point win over Aironi putting another obstacle between the Tigers and the top of the table. The Irish province's five-tries-to-one bonus point win kept them very much in the running and they will hope to repeat the feat in Italy in next time out.

Leinster bolstered their challenge with an 18-13 victory over Bath at The Rec on Sunday that leaves them in control of Pool 3. The usually ruthless Irish side were able to squander some gilt-edged chances and still come away with a priceless victory with the hosts lacking the firepower and discipline to make the most of their rivals' rare off-day. The only try of the game - from wing Matt Banahan - proved good enough for only a bonus point with Leinster No.10 Jonathan Sexton steering his side home in front of Ireland coach Declan Kidney. Glasgow's title hopes are also alive and well having accounted for Montpellier 20-15 at Firhill. The win leaves them second to Leinster in the standings with a repeat win required in France in the return fixture the next requirement.

Saracens lead the English charge having battled past Ospreys in their latest visit to their second home at Wembley Stadium. The high-profile clash vied with the finale of a certain TV talent show being staged at the arena next door but the hosts, and in particular hooker Schalk Brits, displayed more than enough X-Factor on their way to an important 31-26 victory that leave them in charge of Pool 5. But nothing is decided as yet with Biarritz' shock 30-26 loss to Treviso blowing the pool wide open with all to play for - starting this weekend.

The leading Welsh region is Cardiff Blues who maintained their unbeaten start to the tournament with a 25-8 victory over previously unbeaten Edinburgh on Friday night. Fly-half Dan Parks guided the hosts home with a 20-point haul that leaves them in pole position ahead of the return clash at Murrayfield this weekend. But these two sides may not get everything their own way after London Irish produced a superb second half comeback to beat Racing Metro 34-14 and breathe life into their euro campaign.

With everything to play for, expect a flurry of twists and turns in the coming months - starting with Round 4 this weekend.